Potential of muscles to accelerate the body during late-stance forward progression in individuals with knee osteoarthritis

Many individuals with knee osteoarthritis (OA) generate low forward center of mass (COM) acceleration during the late stance phase, consequently making it difficult to walk fast. This study analyzed individual muscle contributions to forward COM acceleration and the muscle potential (i.e., acceleration by unit force) to clarify whether reduced acceleration was related to decreased muscle potential of forward progression by the triceps sure. Twelve individuals with knee OA and 12 healthy age-matched individuals participated in this study. All participants underwent kinetic measurements during normal gait. The simulation involved 92 Hill-type muscle-tendon units with 23 degrees of freedom. We analyzed how each muscle contributed to forward COM acceleration during the 70-100% stance phase using an induced acceleration analysis. Next, the muscle potential of forward COM acceleration was calculated. Our results showed that individuals with knee OA had significantly lower forward COM acceleration with the soleus, gastrocnemius, and iliopsoas muscles compared with controls. Lower muscle potential in the soleus was found in those with knee OA. These findings implied that improving the contribution of the soleus to forward body progression would be effective for increasing the gait speed of those with knee OA during the late stance phase.